Conduit assemblies, such as pipelines and hydraulic circuits, are used to transport an assortment of fluids, such as water, oil, various natural and synthetic gases, sewage, slurry, hazardous materials, and the like. Similar structures are utilized for transmitting electrical and fiber optic cabling across vast expanses of land in establishing telecommunication networks.
Utility pipelines are formed from a variety of materials, including, for example, concrete, plastic (e.g., polyvinyl chloride, polyethylene), and various metallic materials, such as iron, copper, and steel. The outer surfaces of metal pipes, when used in outdoor applications, are typically provided with a corrosion-resistant, protective coating. Such coatings can include a thermoset polymer coating.
In laying pipelines, many of the individual pipes are buried underground. In applications where pipelines are routed underground, passing, for example, under roadways, railroads, buildings, and/or rivers, it is generally not practical to dig a trench in order to bury the pipes. Existing constructions, previously buried utilities, terrain constraints, and topographic restrictions may make trenching economically undesirable and/or physically impracticable.
One trenchless technique employed for burying pipeline assemblies is directional drilling. Directional drilling is generally typified as a process of boring a hole which is characterized in that the course of the bore hole in the earth is in a direction other than vertical—i.e., the axes make an angle with the vertical plane (known as “vertical deviation”), and are directed in the azimuth plane. Conventional directional boring techniques traditionally operate from a boring device or machine that pushes and/or rotates a drill string consisting of a series of connected drill pipes with a directable drill bit to achieve an underground path through which the pipeline assembly can be installed.
Due to practical limitations, the pipeline assembly generated from directional drilling is typically not a single elongated pipe, but rather a plurality of shorter pipes that are subsequently joined together. The pipes are generally joined by welding, such welding typically being performed in the field (therefore commonly known as “field welded joints”). Field welding generally requires any protective coating be removed to bare the underlying steel in the joint region such that the coating materials do not interfere with or denigrate the welding procedure.
One prior art approach for sealing field weld joint regions involves sintering polyethylene material in a mold that is positioned around the joint, thereby formulating a mil coating around the joint. Another approach is to fit an elongated, heat-shrinkable (“recoverable”) sleeve around the joint region. Recoverable sleeves are generally provided with an inner-diameter coating of hot-melt adhesive that is activated through the heat-shrinking process. Both of these prior art approaches, however, are complex, time-consuming, and costly, often requiring several man-hours to create a single seal.
In cases of trenchless pipe laying, such as directional drilling, coating materials of pipes and joints are particularly stressed by enormous abrasion and shear forces. For instance, as the pipes are dragged or pushed through the bore hole, there is likely to be inadvertent contact with gravel, soil, rock formations, and the like. The abrasion stresses and scarring of directional drilling is exacerbated by previous sealing methodologies and seal structures.